The present invention relates generally to annuloplasty prostheses. More particularly, it relates to flexible annuloplasty prostheses for use in conjunction with heart repair procedures, such as annuloplasty bands or rings.
Improvements in cardiopulmonary bypass and myocardial protection and standardization of surgical techniques have lead to increasing interest in valve reconstruction procedures. See, for example, Ormiston J A, Shah P M, Tei C, et al., Size and Motion in the Mitral Valve Annulus in Man, Circulation 1981; 64:113; Dagum P, Green G R, Glasson J R, et al., Potential Mechanism of Left Ventricular Outflow Tract Obstruction After Mitral Ring Annuloplasty, J Thorac Cardiovasc Surg. 1999; 117:472-80; David T E, Armstrong S, Sun Z, Left Ventricular Function After Mitral Valve Surgery, J Heart Dis 1995; 4:S175-80; and Duran C, Perspectives for Acquired Valvular Disease, Advanced Cardiac Surgery, Vol. 4, 1993.
As highlighted by the above, annuloplasty bands and rings have been recognized as being highly useful in a variety of surgical procedures, including mitral and tricuspid valve repair. In general terms, valve annuloplasty is an operation that selectively reduces the size of the valve annulus via an implanted prosthetic device (e.g., annuloplasty band or annuloplasty ring). As implied by the name, an “annuloplasty ring” is a continuous body or ring (e.g., circular- or oval-shaped), whereas an “annuloplasty band” is an elongated body having opposed, unconnected ends. With either construction, the annuloplasty prosthesis is typically characterized as being either flexible or rigid. A rigid annuloplasty prosthetic includes one or more internal stiffening members (e.g., a shaped, metal rod) that enables the prosthesis to return to an original shape after an external force is removed, whereas a flexible annuloplasty prosthesis does not.
Commercial embodiments of annuloplasty prosthetic products include the SJM Tailor™ annuloplasty ring and the SJM Seguin™ annuloplasty ring available from St. Jude Medical of Saint Paul, Minn.; the Carpentier-Edwards annuloplasty rings available from Edwards of Irvine, Calif.; and products sold under the Future, Duran, or Ancore™ trade names available from Medtronic, Inc., of Minneapolis, Minn. A prior art system is described in a brochure entitled “Medtronic Duran Flexible Annuloplasty Systems in Service Guide,” published by Medtronic, Inc., in 2000, Publication No. UC20004685 EN. In addition, annuloplasty prosthesis and surgical methods for implanting prostheses for addressing heart disorders are described in Okada Y, Shomura T, Yamura Yl, et al., Comparison of the Carpentier and Duran Prosthetic Rings Used in Mitral Reconstruction, Ann Thorac Surg 1995; 59:658-63; Duran C M G; Ubago J L M; Clinical and Hemodynamic Performance of a Totally Flexible Prosthetic Ring for Atrio-Ventricular Valve Reconstruction, Ann Thorac Surg 1976; 22:458-63; and Van Rijk-zwikker G L, Mast F, Shepperheyn J J, et al., Comparison to Flexible Rings for Annuloplasty of the Mitral Valve, Circulation, 1990; 82 (Suppl. IV):IV 58-64.
Rigid and flexible annuloplasty prostheses each present certain advantages as possible disadvantages. For example, flexible annuloplasty prostheses can more readily conform to the particular shape and contour of the heart valve annulus being repaired as compared to a rigid product. However, in order to sufficiently support the heart valve annulus being repaired, flexible annuloplasty prostheses are somewhat thicker (e.g., the Duran™ annuloplasty ring and band products have a nominal height or thickness of 3-3.5 mm.)
Additionally, as part of an annuloplasty procedure, surgeons often desire to plicate (i.e., reduce) specific regions of the annulus being repaired. By way of background, implantation of an annuloplasty ring or band includes placing one or more sutures through the annulus tissue, and then coupling or connecting the so-placed suture(s) to the annuloplasty device. A typical suture arrangement entails looping a suture through the annular tissue such that opposing ends or segments of the suture (otherwise extending from the annulus tissue) define a “suture pair”. With this in mind, plication of annular tissue is typically accomplished by establishing a decreased spacing between segments of the suture pair along the annuloplasty prosthesis as compared to the suture pair spacing at the annular tissue. For example, a suture pair can be spaced approximately 5-6 mm in width at the annulus and approximately 4 mm in width at the annuloplasty prosthesis. Subsequently, when the annuloplasty device is cinched against the tissue via the suture pair, the prosthetic forces the suture pair to pull (plicate) annular tissue together between the suture segments. This phenomenon is shown schematically in FIG. 1A in which an annuloplasty prosthesis 10 (shown in side view) is initially secured to annular tissue 12 (shown schematically) by a suture pair 14. In FIG. 1B, the prosthesis 10 is moved against the annular tissue 12, with the suture pair 14 being tied at a knot 16 and causing tissue plication (referenced at 18). Forces exerted by the suture pair 14 on the annular tissue 12 are represented by arrows. Notably, because the suture pair 14 must be tightly bound in order to maintain the tissue plication, tying of the suture pair 14 via the knot 16 also imparts a longitudinally compressive force on the annuloplasty prosthesis 10 as well. Known flexible annuloplasty products, such as flexible annuloplasty bands or rings, have limited longitudinal stiffness, such that when a longitudinal force is applied thereto, the prosthetic may readily buckle or deform along regions subjected to this compressive force as shown in FIG. 1C. A similar phenomena is also observed in non-plicating applications (e.g., simply securing/tying down the suture knot can cause buckling). While the above-described buckling does not appear to negatively affect the efficacy of the implanted device, surgeons may be concerned with the buckled appearance.